// 混合宏，arrow
// 用来实现空角的显示
@mixin arrow(
  $radian,
  $size,
  $borderColor
) {
  @extend %inline-block;
  height: $size;
  width: $size;
  border-left: 1px solid $borderColor;
  border-bottom: 1px solid $borderColor;
  transform:rotate($radian);
}
